nim-libp2p/libp2p/protocols/pubsub/pubsubpeer.nim

268 lines
8.9 KiB
Nim

## Nim-LibP2P
## Copyright (c) 2019 Status Research & Development GmbH
## Licensed under either of
## * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
## * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.
import std/[hashes, options, strutils, tables]
import chronos, chronicles, nimcrypto/sha2, metrics
import rpc/[messages, message, protobuf],
../../peerid,
../../peerinfo,
../../stream/connection,
../../crypto/crypto,
../../protobuf/minprotobuf,
../../utility
logScope:
topics = "pubsubpeer"
when defined(libp2p_expensive_metrics):
declareCounter(libp2p_pubsub_sent_messages, "number of messages sent", labels = ["id", "topic"])
declareCounter(libp2p_pubsub_received_messages, "number of messages received", labels = ["id", "topic"])
declareCounter(libp2p_pubsub_skipped_received_messages, "number of received skipped messages", labels = ["id"])
declareCounter(libp2p_pubsub_skipped_sent_messages, "number of sent skipped messages", labels = ["id"])
type
PubSubObserver* = ref object
onRecv*: proc(peer: PubSubPeer; msgs: var RPCMsg) {.gcsafe, raises: [Defect].}
onSend*: proc(peer: PubSubPeer; msgs: var RPCMsg) {.gcsafe, raises: [Defect].}
GetConn* = proc(): Future[(Connection, RPCMsg)] {.gcsafe.}
PubSubPeer* = ref object of RootObj
getConn*: GetConn # callback to establish a new send connection
codec*: string # the protocol that this peer joined from
sendConn: Connection # cached send connection
connections*: seq[Connection] # connections to this peer
peerId*: PeerID
handler*: RPCHandler
observers*: ref seq[PubSubObserver] # ref as in smart_ptr
dialLock: AsyncLock
RPCHandler* = proc(peer: PubSubPeer, msg: RPCMsg): Future[void] {.gcsafe.}
func hash*(p: PubSubPeer): Hash =
# int is either 32/64, so intptr basically, pubsubpeer is a ref
cast[pointer](p).hash
proc id*(p: PubSubPeer): string =
doAssert(not p.isNil, "nil pubsubpeer")
p.peerId.pretty
proc connected*(p: PubSubPeer): bool =
not p.sendConn.isNil and not
(p.sendConn.closed or p.sendConn.atEof)
proc recvObservers(p: PubSubPeer, msg: var RPCMsg) =
# trigger hooks
if not(isNil(p.observers)) and p.observers[].len > 0:
for obs in p.observers[]:
if not(isNil(obs)): # TODO: should never be nil, but...
obs.onRecv(p, msg)
proc sendObservers(p: PubSubPeer, msg: var RPCMsg) =
# trigger hooks
if not(isNil(p.observers)) and p.observers[].len > 0:
for obs in p.observers[]:
if not(isNil(obs)): # TODO: should never be nil, but...
obs.onSend(p, msg)
proc handle*(p: PubSubPeer, conn: Connection) {.async.} =
logScope:
oid = $conn.oid
peer = p.id
closed = conn.closed
debug "starting pubsub read loop"
try:
try:
while not conn.atEof:
trace "waiting for data"
let data = await conn.readLp(64 * 1024)
trace "read data from peer", data = data.shortLog
var rmsg = decodeRpcMsg(data)
if rmsg.isErr():
notice "failed to decode msg from peer"
break
trace "decoded msg from peer", msg = rmsg.get().shortLog
# trigger hooks
p.recvObservers(rmsg.get())
when defined(libp2p_expensive_metrics):
for m in rmsg.get().messages:
for t in m.topicIDs:
# metrics
libp2p_pubsub_received_messages.inc(labelValues = [p.id, t])
await p.handler(p, rmsg.get())
finally:
await conn.close()
if p.sendConn == conn:
p.sendConn = nil
except CancelledError:
# This is top-level procedure which will work as separate task, so it
# do not need to propogate CancelledError.
trace "Unexpected cancellation in PubSubPeer.handle"
except CatchableError as exc:
trace "Exception occurred in PubSubPeer.handle", exc = exc.msg
finally:
debug "exiting pubsub read loop"
proc getSendConn(p: PubSubPeer): Future[Connection] {.async.} =
## get a cached send connection or create a new one - will return nil if
## getting a new connection fails
##
block: # check if there's an existing connection that can be reused
let current = p.sendConn
if not current.isNil:
if not (current.closed() or current.atEof):
# The existing send connection looks like it might work - reuse it
trace "Reusing existing connection", oid = $current.oid
return current
# Send connection is set but broken - get rid of it
p.sendConn = nil
# Careful, p.sendConn might change after here!
await current.close() # TODO this might be unnecessary
try:
# Testing has demonstrated that when we perform concurrent meshsub dials
# and later close one of them, other implementations such as rust-libp2p
# become deaf to our messages (potentially due to the clean-up associated
# with closing connections). To prevent this, we use a lock that ensures
# that only a single dial will be performed for each peer and send the
# subscription table every time we reconnect.
#
# Nevertheless, this approach is still quite problematic because the gossip
# sends and their respective dials may be started from the mplex read loop.
# This may cause the read loop to get stuck which ultimately results in a
# deadlock when the other side tries to send us any other message that must
# be routed through mplex (it will be stuck on `pushTo`). Such messages
# naturally arise in the process of dialing itself.
#
# See https://github.com/status-im/nim-libp2p/issues/337
#
# One possible long-term solution is to avoid "blocking" the mplex read
# loop by making the gossip send non-blocking through the use of a queue.
await p.dialLock.acquire()
# Another concurrent dial may have populated p.sendConn
if p.sendConn != nil:
let current = p.sendConn
if not current.isNil:
if not (current.closed() or current.atEof):
# The existing send connection looks like it might work - reuse it
trace "Reusing existing connection", oid = $current.oid
return current
# Grab a new send connection
let (newConn, handshake) = await p.getConn() # ...and here
if newConn.isNil:
return nil
trace "Sending handshake", oid = $newConn.oid, handshake = shortLog(handshake)
await newConn.writeLp(encodeRpcMsg(handshake))
trace "Caching new send connection", oid = $newConn.oid
p.sendConn = newConn
# Start a read loop on the new connection.
# All the errors are handled inside `handle()` procedure.
asyncSpawn p.handle(newConn)
return newConn
except CancelledError as exc:
raise exc
except CatchableError as exc:
return nil
finally:
if p.dialLock.locked:
p.dialLock.release()
proc connectImpl*(p: PubSubPeer) {.async.} =
try:
discard await getSendConn(p)
except CatchableError as exc:
debug "Could not connect to pubsub peer", err = exc.msg
proc connect*(p: PubSubPeer) =
asyncCheck(connectImpl(p))
proc sendImpl(p: PubSubPeer, msg: RPCMsg) {.async.} =
doAssert(not isNil(p), "pubsubpeer nil!")
logScope:
peer = p.id
rpcMsg = shortLog(msg)
trace "sending msg to peer"
# trigger send hooks
var mm = msg # hooks can modify the message
p.sendObservers(mm)
let encoded = encodeRpcMsg(mm)
if encoded.len <= 0:
info "empty message, skipping"
return
logScope:
encoded = shortLog(encoded)
var conn = await p.getSendConn()
try:
trace "about to send message"
if conn == nil:
debug "Couldn't get send connection, dropping message"
return
trace "sending encoded msgs to peer", connId = $conn.oid
await conn.writeLp(encoded)
trace "sent pubsub message to remote", connId = $conn.oid
when defined(libp2p_expensive_metrics):
for x in mm.messages:
for t in x.topicIDs:
# metrics
libp2p_pubsub_sent_messages.inc(labelValues = [p.id, t])
except CatchableError as exc:
# Because we detach the send call from the currently executing task using
# asyncCheck, no exceptions may leak out of it
trace "unable to send to remote", exc = exc.msg
# Next time sendConn is used, it will be have its close flag set and thus
# will be recycled
if not isNil(conn):
await conn.close() # This will clean up the send connection
if exc is CancelledError: # TODO not handled
debug "Send cancelled"
# We'll ask for a new send connection whenever possible
if p.sendConn == conn:
p.sendConn = nil
proc send*(p: PubSubPeer, msg: RPCMsg) =
asyncCheck sendImpl(p, msg)
proc `$`*(p: PubSubPeer): string =
$p.peerId
proc newPubSubPeer*(peerId: PeerID,
getConn: GetConn,
codec: string): PubSubPeer =
new result
result.getConn = getConn
result.codec = codec
result.peerId = peerId
result.dialLock = newAsyncLock()